This invention relates to gypsum slurry compositions. Different kinds of molded gypsum objects such as gypsum boards, gypsum plasters and gypsum blocks are produced generally by preparing a gypsum slurry composition containing gypsum, a dispersant and water, pouring it into a mold form and thereafter drying it such that it becomes coagulated and hardened. For such a production process, the gypsum slurry composition is required to have sufficient fluidity and to be capable of exhibiting a superior strength after it has been hardened. This invention relates to gypsum slurry compositions satisfying such requirements.
Examples of gypsum slurry composition of a known kind include those containing not only gypsum and water but also, as a dispersant for gypsum, an anionic surfactant such as lignin sulfonate and naphthalene sulfonate formalin condensation product (such as described in Japanese Patent Publication Tokkai 1-188448), a water-soluble vinyl copolymer obtained by copolymerizing monoester of maleic acid, α, β-unsaturated monocarboxylic acid and (meth)allyl ether having polyoxyalkylene group (such as described in Japanese Patent Publication Tokkai 2002-3257), a water-soluble vinyl copolymer obtained by copolymerizing α, β-unsaturated monocarboxylic acid or its anhydride and alkenyl ether such as allyl ether with polyoxyalkylene group (such as described in Japanese Patent Publication Tokkai 11-314953) or a water-soluble vinyl copolymer obtained by copolymerizing ester of α, β-unsaturated monocarboxylic acid with polyoxyalkylene group, α, β-unsaturated monocarboxylic acid and allyl sulfonic acid (such as described in Japanese Patent Publication Tokkai 8-217505 and U.S. Pat. No. 6,527,850).
These prior art gypsum slurry compositions are not satisfactory because their fluidity is not sufficient, unstable bulky air bubbles are likely to be generated at the time of their production and the molded products obtained therefrom are not sufficiently strong probably due to such air bubbles that are introduced into the hardened molded object.